Pharyngitis is the inflammation of the pharynx, a region in the back of the throat. In most cases it is quite painful, and it is the most common cause of a sore throat. Most of the acute cases are caused by viral infections (40-80%), with the remainder being caused by bacterial infections, fungal infections, or irritants such as pollutants or chemical substances.
Amongst the bacterial organisms that cause the acute pharyngitis, the most common are Group A beta-haemolytic Streptococci. The other types of bacteria causing this disease are non-Group A beta-haemolytic streptococci and Fusobacterium, though less common.
The bacterial pharyngitis caused by streptococci will be called streptococcal pharyngitis here onwards. The typical symptoms of streptococcal pharyngitis are soar throat, fever with temperature above 38° C., tonsillar exudates, and enlarged tender cervical lymph nodes. The minor symptoms could be headache, nausea, vomiting, abdominal pain, muscle ache, scarlantiniform rash and petechiae on the palate. It is contagious by means of contact.
Though symptoms like red eyes, hoarseness, runny nose or mouth ulcers are the first leads for the diagnosis of streptococcal pharyngitis, they are not conclusive, more so in the absence of fever. The confirmatory tests can be either throat culture or the Rapid Strep Test. Throat culture involves taking a swab of the infected area or the exudates and culturing the sample on a suitable culture medium. This test is more reliable, specific for Group A beta-haemolytic Streptococci with high sensitivity and is affordable. The Rapid Strep test or Rapid Antigen Detection Test works by detecting the presence of GAS (Group A Streptococci) in the throat of a patient by responding to GAS-specific antigens on a throat swab. When the sample is applied on an antigen incorporated film strip, it changes color if the test is positive. It gives the results within several minutes.
There is a downside to both these testing procedures. In case of the throat culture, the results take at least 48 hours to be revealed and a culture requires special facilities. This will delay the administration of necessary medication given to the patient that will avoid further complications like the rheumatic fever, and local suppurative complications. In the case of Rapid Strep Test, the downside is the high cost of the film strips that contain the antibodies for GAS antigen incorporated in them. Although, rapid strep test cannot distinguish GAS infection from asymptomatic carriage of the said organism, it is sufficient to provide immediate symptomatic treatment.
In an article published by Shaikh et al. in Pediatrics 2012 March, 160(3): 487-493, titled ‘Accuracy and Precision of the Signs & Symptoms of Strep. Pharyngitis in children—a Systematic Review’, it was stated that no individual symptoms or signs were effective in confirming streptococcal pharyngitis. It was suggested that the symptoms and signs, either individually or combined into predictive indicators, cannot be used to definitely diagnose or rule out streptococcal pharyngitis.
In another article published by Maltezou H C et al. in J. Antimicrob. Chemother. 2008 December 62(6):1407-12 dol:1093/jac/dkn376.Epub 2008 Sep. 11, titled ‘Evaluation of rapid antigen detection test in the diagnosis of streptococcal pharyngitis in children and its impact on antibiotic prescription’, the usefulness of Rapid Antigen Detection Test (RADT) in the diagnosis of streptococcal pharyngitis in children and its impact on antibiotic prescription was stated to be studied and that it was found that RADT provided appropriate guidance to treat strep throat infections and reduce the need for unnecessary cultures and usage of antibiotics.
In an article published by Forward K V et al. in Canadian J. Infect. dis. Med. Microbiology 2006, July 17(4)221-3, titled ‘A comparison between the strep A Rapid Test device and conventional culture for the diagnosis of strep A Pharyngitis’, stated that it was found that in cases of strep pharyngitis the rapid strep test has a sensitivity of only 72%.
In the Text book of Pediatrics, 13th edition—Streptococci pages 577-578, authored by Richard Behrman et al., the lesions caused by the streptococcal pharyngitis were described to be characterized by edema, hyperemia and infiltration of polymorphonuclear leukocytes.
Joshi D et al. have disclosed in their article titled ‘Diagnostic accuracy of reagent strip to determine CSF chemistry & cellularity’ published in J. Neuroscience Rural Practice 2013 April 4(2):140-5. Dol:10 4103/0976-3147.112737, the usage of urine reagent strip for semi-quantitative assessment of protein, glucose and presence of LE in CSF thus, suggesting that the existing reagent strip can be used to diagnose meningitis in low resource settings.
Farahmed. F et al. disclosed in their publication titled ‘Diagnosis of spontaneous bacterial peritonitis in children by reagent strip’ in Actamed Iran, 20B, March 16; 51(2):125-8, their study on the effectiveness of dipstick (LE & nitrite) for diagnosis of bacterial peritonitis in cirrhotic patients. It was found that the sensitivity, specificity, positive and negative predictive value of LE reagent might prove as a rapid bedside diagnostic test for diagnosis of spontaneous bacterial peritonitis in cirrhotic patients.
Kelly and her colleagues, according to their article titled ‘LE in rapid diagnosis of pediatric septic arthritis and found that LE test is very useful for rapid diagnosis of septic arthritis’ published in Med Hypothesis 2013, February 80(2):19-3 dol 10 1016/May 2012 11026 EPub 2012 Dec. 19, studied the usage of LE in rapid diagnosis of septic arthritis and found that LE test is very useful for rapid diagnosis of septic arthritis.
The ESCMID Sore throat Guideline Group consisting of Pelucchi. C et al., in their article titled ‘Guideline for the management of acute sore throat’ published in J. Clin. Microbiol. Infect. 2012 Apr. 18, supplement 1:1-28, dol: 10.1111/j.1469-0691.2012.03766, outlined the guidelines to diagnose and treat patients with a strep throat. It was suggested that the Centor Scoring should be used along with Rapid Antigen Test, and recommended that antibiotics may not be used for Centor Scores of 0-2 as suppurative complications were infrequent with these scores.
From an extensive study and understanding of the prior art, it was found that the throat culture, though the best and specific method, is a very slow process to confirm the streptococcal infection. The Rapid Strep Test presents an alternative to the throat culture for rapid results which can be an important strategy to reduce unnecessary antibiotic use or the delay in the treatment, thus avoiding further complications. However, this test can be costly and may not be affordable in low resource settings.
It was also found in the prior art that early polymorphonuclear leukocyte response in the pharyngo-tonsilar region which results in the release of leukocyte esterase in the lesions in the throat is caused by the streptococcal pharyngitis.
The present invention presents a possible alternative method to the Rapid Strep Test that can be performed at a lower cost but with equal efficiency to the Rapid Strep Test in terms of fast delivery of results. The present invention is based on the fact that the streptococcus pharyngitis causes lesions that result in the release of leukocyte esterase.